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Automated design system for drawing dies Bor-Tsuen Lin *, Shih-Hsin Hsu Dept. of Mechanical and Automation Engineering, National Kaohsiung First University of Science and Technology, Kaohsiung 824, Taiwan, ROC Abstract This paper describes an automated design system for drawing dies. Taking advantage of pre-built design knowledge base and data- base, this system is able to output designs of the main components of a drawing die, such as upper dies, lower dies and blank holders, upon users input of design information of blank lines, die faces, punch open lines, press data, and types of subcomponents such as hooks, guides, and stopper seats. This die design system is built on top of CATIA V5, and makes use of its built-in modules, including Part Design, Automation and Scripting, and Knowledge Advisor. Our system also includes an inference engine, and user interfaces. We use drawing dies for trunk lid outer panels and engine hood outer panels as concrete examples to showcase the power of our system. Experimental results show that our system can improve the design quality and reduce the design time and cost. ? 2007 Elsevier Ltd. All rights reserved. Keywords: Drawing dies; Design system; CAD; Knowledge base; Parametric modeling 1. Introduction Press parts, such as frames, bodies, and doors, are widely used in the automotive industry. In order for a man- ufacturer to survive in todays competitive market, the development process of a vehicle needs to be carried out in an effi cient and eff ective way in order to meet customers expectation. Die design is part of the critical path of the entire development process. There are three categories of stamping dies, based on their functionalities: drawing dies, trimming dies, and bending dies. Since most stamping dies for automotive sheet metals are big and complex, the stamping die design process is very time-consuming. Recently, as a result of the fast development of com- puter technology and of 3D CAD software, 3D CAD soft- ware has been widely used in designing drawing dies. A solid model off ers users an intuitive and concrete view of the die in design, which fundamentally reduced design time. However, most 3D CAD software only provides users with geometric modeling functions for constructing a solid model, but fails to off er a powerful design knowledge base, which is essential to assist engineers in accomplishing the design task. As a result, the developments of automated, knowledge base and intelligent design systems are studied by research- ers from around the world. Myung and Han (2001) devel- oped an expert system based on a confi guration design method. This system allows users to design mechanical products in a 3D environment. Roh and Lee (2006) pro- posed a hull structural modeling system for ship design, which was developed using C+ and built on top of 3D CAD software. Lee, Hsu, and Su (1999) developed a para- metric computer-aided die design system for cold forging using Auto-LISP. In order to make the modeling process more effi cient, Kong et al. (2003) developed a Windows- native 3D plastic injection mold design system based on Solid Works using Visual C+. Chu, Song, and Luo (2006) developed a Computer aided parametric design sys- tem for 3D tire mold production in CATIA using CAA. In the stamping die design area, Cheok and Nee (1998) developed a knowledge based strip layout design system in AutoCAD. Taking advantage of neural network and CAD 0957-4174/$ - see front matter ? 2007 Elsevier Ltd. All rights reserved. doi:10.1016/j.eswa.2007.01.024 * Corresponding author. Tel.: +886 76 6011000; fax: +886 7 6011066. E-mail addresses: bt_.tw (B.-T. Lin), u9314805 .tw (S.-H. Hsu). Available online at Expert Systems with Applications 34 (2008) 15861598 Expert Systems with Applications software, Pilani, Narasiman, Maiti, Singh, and Date (2004) proposeda methodforautomaticallygeneratingan optimal die face design based on die face formability parameters. Ismail, Chen, and Hon (1996) developed a fea- ture-based progressive press tool using cheap CAD soft- ware. Based on sheet metal operations, Singh and Sekhou (1999) developed a punch machine selection expert system, which was built in AutoCAD and used AutoLISP. Tisza (1995) developed an expert system for detail process plan- ning of metal forming in AutoCAD. Though the design process of drawing dies is extremely complex and requires a great deal of professional knowl- edge, the purpose of this paper is to develop an automated design system for drawing dies. Taking advantage of well- organized die design knowledge base and database and an integrated 3D CAD environment, our system is able to out- put designs of the main components of a drawing die, such as upper dies, lower dies and blank holders, upon users input of design information of blank lines, die faces, punch open lines (POL), press data, and types of subcomponents U-groove Triangle Rib Guide Stopper Seat Hook Auxiliary Plate Dieface Thickness Lower Die Size Hook Guide Cushion Pin Seat Stopper Seat Blank Holder Size Panel Guide Seat Avoid Structure Safety Area Guide Safety Area Cushion Pin Hole Stopper Seat Hook U-groove Key-groove Auxiliary Plate Triangle Rib Dieface Thickness Lower Die Size Avoid Structure Fig. 1. Structure of main components for a drawing die. (a) Upper die. (b) Blank holder. (c) Lower die. B.-T. Lin, S.-H. Hsu / Expert Systems with Applications 34 (2008) 158615981587 such as hooks, guides, and stopper seats. Experimental results show that our system can generate high quality design of main components of a drawing die in an effi cient way. 2. Drawing die design 2.1. Drawing die confi guration Drawing is a process of cold-forming a fl at precut metal blank into a hollow vessel without excessive wrinkling, thin- ning, or fracturing (Wick, Benedict, 33 categories subcomponents with 42 diff erent types are listed in our system. The understanding of the relationship among various subcomponents is vital to obtain an appropriate design process for each of the subcomponents. Detailed modeling processes for each subcomponent, as well as geo- metric operationsused insuchprocesses, areavailableinthe knowledge base. Also, design guidelines and 3D diagrams with design parameters, itemized text, and formulas are stored as e-books for training, debugging, and reference purposes. 3.4. The design database The design database off ers subcomponent specifi cations and press machine specifi cations. The subcomponent spec- ifi cations specify the sizes of each of the subcomponents, while the press machine specifi cations specify size of the bolster, maximum and minimum of the die height, maxi- mum die width, positions and sizes of T grooves and cush- ion pin holes, and cushion pin strokes. The design database has 44 types of subcomponent design specifi cations, which fall into 33 categories. The design specifi cations for each of the subcomponents are illustrated in 2D diagrams. In addition, each diagram is accompanied by a table that summarizes the related shape parameters and standard sizes. The design database off ers four sets of press machine specifi cations, which are pre- sented in 2D diagrams. All information in the design data- base is stored as e-books for easy access. 3.5. CAD software Our system is developed based on CATIA V5 CAD soft- ware in the Windows XP operating system. This system is designed to be used in a PC, and is developed using the CATIA softwares built-in modules. The Part Design mod- ule is responsible for controlling and executing the process of constructing 3D models. Therefore, this module is used to build the inference coordinator. The Knowledge Advisor Fig. 8. The layer tree of drawing die. 1592B.-T. Lin, S.-H. Hsu / Expert Systems with Applications 34 (2008) 15861598 module allows users to embed related knowledge into the design, which increases the productivity of design engi- neers. The subcomponent selector takes advantage of the Formula Editor and Rule Editor functions, while the shape calculator uses the Design Table function. The Automation and Scripting module off ers a user-customized interface for CAD software. The model generator makes use of Visual Basic for Application (VBA) to develop programs for gen- erating solid models. The user interface also uses VBA to construct alphanumeric and graphic input interfaces. 4. Modeling process of the automated design system This system is built on top of the CATIA CAD system, and takes advantage of various CATIA built-in modules. Upon users input of the design information, our system Fig. 9. Sample die. Fig. 10. Program design. B.-T. Lin, S.-H. Hsu / Expert Systems with Applications 34 (2008) 158615981593 is able to automatically generate the solid model design of main components of a drawing die in an effi cient and fl exi- ble way. Fig. 5 shows the modeling process. Each step of the modeling process is detailed in the following sections. Fig. 11. Interface for replace procedure of graphic data. (a) Load a graphic data. (b) Active replace window. (c) Ready for update. 1594B.-T. Lin, S.-H. Hsu / Expert Systems with Applications 34 (2008) 15861598 4.1. Die structure analysis Drawing dies for the automotive industry are very large, and have very complicated structures. Moreover, each sub- component has its own functionality. Therefore, before developing the design system, we collected various struc- tures of drawing dies for automotive sheet metals, and ana- lyzed their architectures and functions. Fig. 6 shows a classifi cation of the subcomponents of a typical drawing die based on their functionality. The parameterized die design system treats the change- able dimensions of a die as parameters, and generates the fi nal design by assigning appropriate values to each of the parameters based on design formulas, constraints and tables derived from the design guidelines and specifi cations. However, certain data and subcomponents, such as press machines, hooks, guides, and stopper seats, cannot be designed simply by changing the design parameters because of the diversity of their structures. Therefore, we pre-build the interfaces and structures of a sample die for all subcom- ponents that share the same functionality based on design guidelines and specifi cations. 4.2. Design process standardization The purpose of design process standardization is to pro- vide a systematic way of designing dies. Since the CAD sys- tem has its own modeling process, the size and position of design subcomponents cannot be determined until the size and position of certain subcomponents are fi xed. A stan- dardized design process, as shown in Fig. 7, is generated based on the design guidelines and specifi cations of each of the subcomponents, as well as the cause-and-eff ect rela- tionships among these subcomponents. This standardized process is used to guide the design of main components of sample dies, such as their structures and initial sizes, as well as the initial sizes and positions of each subcompo- nent on a main component. 4.3. Sample die construction Once a standardized design process is obtained, a fea- ture layer tree and sample dies are developed based on the design process, as shown in Figs. 8 and 9. A typical die face consists of thousands of surfaces. In order to ensure the stability of a sample die, simple die faces are used to construct sample dies. Since various subcompo- nents of a drawing die can share a common functionality, all possible subcomponent structures of a function must be pre-constructed when constructing sample dies. When constructing a solid model of a die, only the selected sub- components should be activated. All unselected subcompo- nents should be deactivated. When constructing sample dies, design engineers should make use of all available parameters and pre-set sizes. The number of parameters has adirect impact on the design fl ex- ibility. In most cases, the number of parameters decreases in the design process, which makes programs more concise. Therefore, appropriate number of parameters is vital to the entire design process. All of the changeable dimensions are treated as parameters, whose values can be changed based on design requirements. Since the values of the dimension parameters cannot be non-positive, all possible situations should be taken into consideration to avoid any potential problems, especially when there are cause-and- eff ect relationships among the various subcomponents. 4.4. Parameter settings There are hundreds of parameters in our automatic design system, which demands a systematic naming schema so that parameters can be well managed to facilitate coding and debugging. The name of a parameter used in our sys- tem consists of two parts: the name of the part to which the parameter belongs, and the name of the dimension. Based on the parameters functionality, they can be divided into shape parameters and position parameters. Shape parameters can be further classifi ed as dependent parametersandindependentparameters.Independent Fig. 12. Alphanumeric data interface. B.-T. Lin, S.-H. Hsu / Expert Systems with Applications 34 (2008) 158615981595 parameters only need to meet the design guidelines, while dependent parameters are determined by both the design specifi cations and any relevant independent parameters. Taking the bolt type hook shown in Fig. 3 as an example, the diameter of the hook bolt, d, is an independent param- eter, while the other measures, such as Y, X, r, t, l, and R, are dependent parameters. 4.5. Programming Once the parameters have been identifi ed, the relation- ships among various parameters need to be formulated based on design guidelines and specifi cations. These rela- tionships are further converted into programs. Programs are divided into three levels in order to facilitate the design process. Taking the bolt type hook as an example, the purpose of the fi rst level is to select subcomponents based on design guidelines. This level of program takes advantage of two built-in modules of CATIA V5, Rule Editor and Formula Editor, to convert design guidelines into constraints and formulas respectively, which are used to determine the quantity, position and size of subcomponents, as shown in Fig. 10a and b. The second level of the program is responsible for calcu- lating the values of shape parameters of the die. This level takes advantage of the built-in modules of CATIA V5 to construct the design table of the die based on the design specifi cations of each subcomponent, so that this level of the program can use the design table and related indepen- dent to determine dependent parameters, as shown in Fig. 10c. The third level of the program is used to construct of the model. Written by VBA, this level of program is used to provide a modeling procedure of subcomponents based on determined the type and size of aforementioned two lev- els, as shown in Fig. 10d. 4.6. User interfaces User interfaces allow users to accomplish the design process in an intuitive and interactive way. The user inter- faces used in our system can be classifi ed into two categories. Fig. 13. Design process of the proposal system. (a) Sample die. (b) Graphic data interface. (c) Alphanumeric data interface. (d) Drawing die for trunk lid outer panel. 1596B.-T. Lin, S.-H. Hsu / Expert Systems with Applications 34 (2008) 15861598 The fi rst category is used to input graphic information, suchasblanklines,diefacesandPOLs.Thissetofinterfaces is using Replace, which is a built-in function of CATIA V5. Following are the procedures for replacing sample graphic information. First, start the automated design system, and load the desired graphic information into the design envi- ronment. Click on the layer tree representation of the sam- ple graphic information, as shown in Fig. 11a, and open the Replace window, as shown in Fig. 11b.Select the desired graphic information of the die and click OK. The color of the die turns to red when it is being updated, as shown in Fig. 11c. The second category is used to input alphanumeric information, such as types of press data, guide mechanism, and hooks and stopper seats, as shown in Fig. 12. Imple- mented using VBA, a drop-down menu allow users to select the appropriate types of subcomponents for the die. Design engineers only need to select the desired press machine and types of subcomponents, and click OK; the system is able to automatically complete the design. 5. Case study We use the design of drawing dies for a trunk lid outer panel as a concrete example to showcase the power of our system. A standard structure diagram of sample dies is dis- played when the system starts, as shown in Fig. 13a. Upon receiving graphic information from the user, our system uses CATIAs built-in Replace function to replace the gra- phic information using the layer tree of the sample die, as shown in Fig. 13b. Then, users begin to input alphanumeric information, such as the types of press machines, guide mechanism,hooks,andstopperseats,asshownin Fig. 13c. After users click OK, our system begins to gener- ate the design based on the design processes, guidelines and specifi cations. The fi nal design of the drawing die is shown in Fig. 13d. Fig. 14 presents a comparison of two diff erent drawing dies, a drawing die for trunk lid outer panels and a drawing die for engine hood outer panels, to show that our system can handle a wide range of designs. 6. Conclusions and future works This paper presents an automated design system for drawing dies, which is built on top of CATIA CAD soft- ware. Upon receiving the initial design information from design engineers, such as blank lines, die faces, POLs, and press data, as well as the types of hooks, guide mech- anism, and stopper seats, the system is able to automati- cally generate the fi nal design of main components of the die, such as upper dies, lower dies, and b